The present invention relates to a heat transfer image-receiving sheet used in combination with a heat transfer sheet.
Among various heat transfer techniques so far known in the art, there is a sublimation type of transfer system wherein a sublimable dye as a recording material is carried on a substrate sheet such as paper or a plastic film to make a heat transfer sheet, which is in turn overlaid on a heat transfer sheet dyeable with a sublimable dye, for instance, a heat transfer sheet comprising paper or a plastic film having a dye-receiving layer on its surface to make various full-color images thereon.
In such a system, the thermal head of a printer is used as heating means to transfer three-, four- or more-color dots onto the heat transfer image-receiving sheet by quick heating, thereby reproducing full-color images of manuscripts with said multicolor dots.
When the heat transfer image-receiving sheet used with such a sublimation type of heat transfer system as mentioned above is required to form a light reflecting image, as is the case with generally available prints or photographs, it is formed of an opaque substrate sheet such as a paper or synthetic paper sheet having on its surface a dye-receiving layer of a resin capable of being well-dyed with a dye. When it is required to provide a light transmitting image which is used with an overhead projector (hereinafter OHP for short), etc., on the other hand, it is formed of a transparent sheet such as a polyester film having thereon such a dye-receiving layer as referred to above.
When imaging is carried out with either one of such heat transfer image-receiving sheets, there is an increase in the temperature prevailing in the printer. This poses troubles or problems such as curling of the heat transfer image-receiving sheets or degradations of their slip properties and blocking resistance, which result in sheet jamming or multiple feeding of several sheets at one time.
The curling problem may be solved by forming a curlproof layer of a suitable resin on the back side of the heat transfer image-receiving sheet. However, if such image-receiving sheets, placed one upon another, are fed through a sheet feeder unit of the printer, then the multiple feeding problem arises, because the coefficient of friction between the curlproof layer of the sheet above and the dye-receiving layer of the sheet below is high. This problem may be solved to some extent by adding a slip agent such as silicone oil to the curlproof layer. However, the silicone oil tends to bleed through the image-receiving sheet or otherwise pass into the dye-receiving sheet below, posing various problems.
It is therefore a first object of this invention to provide a heat transfer image-receiving sheet which is so improved in terms of in-printer slip properties, blocking resistance and curling resistance that it can form a high-quality image without causing any printing trouble.
It is here noted that images obtained with the heat transfer techniques excel in clearness, color reproducibility and other factors and so are of high quality comparable to that of conventional photographic or printed images, because the colorant used is a dye. Especially when imaging is carried out with transparent films or sheets for OHPs, a transmission type of image of improved clearness and high resolution can advantageously be projected.
The image-receiving sheet for OHPs is provided with a detection mark for positioning. However, conventional detection marks have been formed of black, white or silver inks, all having high shielding properties. As a result, an image projected on a screen becomes dull, since the detection mark throws a black shadow on the screen.
Another problem with the image formed with OHPs is that an OHP film is so curled by the heat generated from a projector's light source that it is troublesome to handle and the projected image is distorted.
It is therefore a second object of this invention to provide a transparent type of heat transfer image-receiving sheet which is free from the above-mentioned problems of the prior art and which provides an attractive image at the time of projection and is not curled in use.